Asian Journal of Research in Biochemistry

This study investigated the toxicological effects of ethanolic leaf extract of turmeric (Curcuma longa) on the mortality and organ morphology of African catfish (Clarias gariepinus) fingerlings. Two hundred healthy specimens (mean length 3.40 ± 1.2 cm; mean weight 2.26 ± 1.25 g) were exposed to graded concentrations of the extract (0, 20, 22, 24, 26, 28 mg/L) for 96 h. The 96 hours LC50 was given at 22 mg/L representing a log transformed concentration of 1.34 mg/l a point where 50 % of the test organisms would be killed at the end of the experiment. No mortality or abnormal behavior was observed in the control group, whereas exposed fish exhibited concentration-dependent mortalities and behavioral changes, including erratic swimming, air gulping, loss of reflex, hyperactivity, and skin discoloration. Water quality parameters (pH and dissolved oxygen) significantly (P < 0.05) declined with increasing extract concentration. The significant decline in DO affect the survival of the fingerlings, hence the mortality recorded during the study.  Histopathological examination revealed progressive damage in the gills, including epithelial disintegration, lamellar fusion, and structural collapse, as well as hepatic alterations such as hepatocellular necrosis, vacuolation, and blood cell rupture. These changes indicate severe impairment of respiratory and metabolic functions at higher exposure levels. Although turmeric is globally recognized for its nutraceutical, antimicrobial, and immunostimulatory properties, this study demonstrates that excessive concentrations can compromise fish health, nutrient assimilation, and survival. Safe inclusion limits are therefore necessary if turmeric is to be applied in aquaculture as a feed additive. Future studies incorporating biochemical and molecular biomarkers are recommended to better define its risk–benefit profile in fish culture.